Under normal circumstances, the liver is able to regenerate itself following damage; however, this ability is lost following ethanol consumption. The liver's regenerative ability depends on the coordinated signaling interactions between parenchymal (hepatocytes) and non-parenchymal (hepatic stellate cells, Kupffer cells) cell types. MicroRNAs, a class of small (~22 nucleotides) non-coding RNAs, play many important roles in maintaining proper cellular function. Therefore, it is likely that ethanol-induced disrupton of normal microRNA regulation of cell signaling will affect the liver's ability to undergo regeneration. My research will focus on the role of microRNAs specifically in hepatic stellate cells, which produce a number of cytokines, growth factors, and extracellular matrix proteins important for normal liver regenerative function. In order to study this system, I have developed a computational model of hepatic stellate cell activation which includes a process for introducing negative regulation of target genes by two microRNAs of interest-miR-21 and miR-146a. The model is able to describe certain changes that occur in transcription factor and microRNA levels during hepatic stellate cell activation, but expansion of this model with the introduction of furthr microRNA regulatory networks would provide additional information on the dynamics of expression during activation and re-normalization upon cessation of stimulating signals. Therefore, the goal of this project is to characterize the regulatory microRNA-gene networks involved in hepatic stellate cell activation and understand how their dysregulation by alcohol adaptation contributes to impaired liver regeneration by testing three hypotheses: (1) microRNA balances are altered in a hepatic stellate cell-specific manner, (2) hepatic stellate cell activatin and quiescence is controlled by a shift in distributions of microRNA networks, and (3) inhibition of miR-21 results in a shift from an anti- to pro- regenerative phenotype as the result of altered cellular signaling. These hypotheses will be tested using a variety of in vivo and in vitro approaches, including rat models of alcohol adaptation, cell culture, single-cell capture and analysis, and microarray studies. In addition, the existing model of hepatic stellate cell activatin will be expanded, and in silico studies will be used to predict changes in microRNA and target gene expression in response to stimulating factors. Experimental validation will help tease out the mechanisms of stellate cell activation and its role in regeneration, as well as further refine the model. We expect to identify which microRNAs play a key role in stellate cell activation, what cellular processes they regulate, and how their dysregulation in response to ethanol can lead to an impaired regenerative ability.